This proposal is designed to elucidate the mechanism(s) of action of the neural influences on the renal tubule--what are the specific neurotransmission steps at the level of the renal tubular epithelial cell whereby chages in renal nerve activity result in alterations in tubular transport? Specific studies using renal micropuncture and microperfusion techniques will be performed to identify the cellular locus of a site of action (peritubular or luminal cell membrane) and to characterize it pharmacologically (alpha or beta adrenergic, dopaminergic). Additional experiments will examine the role of the renal nerves in th compensatory response of the contralateral kidney to an intervention which alters the function of the other kidney; specific studies using renal nerve activity recordings, selective renal denervatin and/or spinal cord section will be performed to evaluate the role of the renal nerves in the contralateral neural compensatory response to ureteral occlusion or exclusion of the kidney from the circulation. These studies will provide a sharper focus on the mechanism of action of neural influences on the renal tubule. The localization of the site and the characterization of the mechanism of this action will serve to expand the framework of our understanding of the understanding of the neuroadrenergic innervatin of the renal tubule.